1. Field of the Invention
This invention relates to scroll fluid apparatuses and, more particularly, to a shaft seal structure in a scroll fluid apparatus of a rotating drive/driven scroll type comprising a drive and a driven scroll, the shaft seal structure being provided in a discharge part for discharging compressed fluid, as well as a scroll fluid apparatus in which the engagement between wraps and an opposed scroll plate is adjustable.
2. Description of the Prior Art
FIG. 11 shows a prior art scroll fluid apparatus. The apparatus comprises a stationary scroll 110 secured to an end face of a frame 140. The stationary scroll 110 has vertically an involute wrap 113 which is provided in a concave space defined by a peripheral wall 111 with a suction port 116 formed therein, and also has a discharge port 117 provided substantially at a central position for discharging compressed fluid.
In a concave space defined by the frame 140, a revolving scroll 120 is accommodated and has an involute wrap 121 formed vertically on a scroll body having an end surface in contact with an end surface of the peripheral wall 111. The involute wrap 121 has substantially the same shape as the wrap 113 of the stationary scroll 110. The wraps 113 and 121 are engaged with each other in a 180-degree out-of-phase relation to each other.
Self-lubricating seals 131 are each fitted in a concave groove formed in the end surface of each of the wraps 113 and 121 of the scrolls 110 and 120 in contact with the other scroll. The wraps 113 and 121 thus undergo sliding by lubricant-free oil. A ring-like self-lubricant free seal 132 is fitted in a concave groove formed in the end surface of the stationary scroll 110 in contact with the corresponding end surface of the revolving scroll 120, whereby the concave space defined by the peripheral wall 111 noted above is thus sealed gas-tight from the outside.
The frame 140 axially supports a drive crankshaft 141 with a pulley 142 provided at one end, and also supports three driven crankshafts 150 spaced apart at an interval of 120.degree. with respect to the main drive shaft 141.
The crankshafts 141 and 150 have their eccentric end portions 411 and 501 supported for rotation via bearings 143 and 155 in an inner frame 125 which is integral with the revolving scroll 120.
Rotation of the drive crankshaft 141 causes revolving of the driven crankshafts 150 in correspondence to the eccentricity of the drive crankshaft 141, whereby the revolving scroll 120 undergoes revolving about the wrap center of the stationary scroll 110 with a predetermined radius of revolving while not in rotation.
In the prior art scroll fluid apparatus as described above, the parallelness and clearance of the revolving scroll 120 with respect to the stationary scroll 110 should be accurately adjusted so that the revolving scroll 120 can revolve with adequate accuracy of wrap engagement. Without these accurate adjustments, fluid may leak through sealed spaces. In addition, the wraps and the opposed sliding surfaces may be brought into contact with one another, resulting in noise generation and abnormal wear. Moreover, partial contact of the wraps is liable, thus increasing the drive power and reducing the durability of the bearings.
In the frame 140, ball bearings 151 are fitted for movement in the thrust direction on the driven crankshafts 150, which are provided at an interval of 120.degree. with respect to the drive crankshaft 141. The position of the ball bearings 151 in the thrust direction is made adjustable by turning outside race retainers 160 in plus or minus directions. The race retainers are screwed on the driven crankshafts 150 and can be turned in either direction.
The outside race retainers 160 slightly project from the end surface of the frame 140, and can be locked by lids 146.
The driven crankshafts 150 have their eccentric portions 501 supported via bearings 155 in the inner frame 125 integral with the revolving scroll 120.
In this embodiment, the thrust displacement volume between the sliding surface 120a of the revolving scroll 120 and the frame end surface 140a is adjustable by turning the outside race retainer 160 in plus or minus directions.
In the above prior art scroll fluid apparatus, for the adjustment of thrust displacement volume between the sliding surface 120a of the revolving scroll 120 and the frame end surface 140a, the bearings 155 which are provided near the outer periphery of the revolving scroll 120 are advanced and retreated in the thrust direction by turning the outside race retainers 160 in either a plus or a minus direction. Therefore, some of the bearings 155 may be advanced or retreated excessively, while the others are advanced or retreated insufficiently, resulting in an increase of the drive power due to partial contact of wraps or durability reduction of the bearings.